Law of Conservation of Mass
Law of Definite Proportions
Law of Multiple Proportions
Atom
Thomson’s Cathode-Ray Tube Experiment
Millikan’s Oil Drop Experiment
Rutherford’s Gold Foil Experiment
Periodic Table of the Elements
Atomic Number (Z)- the atomic number is unique for each element- provides the number of protons that an element has
6
CCarbon
12.0107
- IF the element is neutral, it also provides the number of electrons
Atomic #
Atomic symbol
Mass Number
- the mass number is the number of protons and neutrons in a particular element
6
CCarbon
12.0107
- To find the number of neutrons subtract the number of protons (atomic number) from the mass number.
Mass Number
- the atomic mass of the element in amu (atomic mass unit)
6
CCarbon
12.0107
26
FeIron55.845
36
KrKrypton
83.798
ExamplesFind the number of protons, electrons, and neutron in the following:
Protons:
Electrons:
Neutrons:
Ions- elements or group of elements that have gained or lost electrons.- if an element loses electrons it is a positive ion or cation.- if an element gains electrons it is a negative ion or an anion.
Examples:sodium (Na)p -e -n -
oxygen (O)p -e -n -
sodium ion (Na+) p -e -n -
oxygen ion (O2-)p -e -n -
Isotopes- atoms of the same element with different masses.- mass numbers will be different.- since mass #’s are different, the number of neutrons are not the same.
Some isotopes have unique names, some do not.H-1 (hydrogen) H-2 (deuterium) H-3 (tritium)
C-12 (carbon 12) C-13 (carbon 13) C-14 (carbon 14)
Examples:carbon-12 carbon-14 p - p - e - e -n - n -
Average Atomic Mass- weighted average of atomic masses of naturally occurring isotopes of an element.
Example: Copper
copper-63 – 62.929598 69.17% of all coppercopper-65 – 64.927793 30.83% of all copper
What is the weighted atomic mass of copper? 63.546 amu
Average Atomic Mass
Avogadro’s Number- the number of particles in exactly one mole of a pure substance.- 6.022 x 1023 particles (atoms or molecules)
The Mole (mol)- the amount of a substance that contains as many particles as there are atoms in exactly 12 g of carbon-12.- the mole is a counting unit
Molar Mass- mass of one mole of a pure substance- numerically it is equal to the atomic mass of the element or compound.- the unit used is g/mol.- when using molar mass, use 4 significant figures!
The Mole
Avogadro’s Number
Molar Conversions- molar mass and Avogadro’s number can be used as conversion factors to convert from one unit to another
1 mol = 6.022 x 1023 atoms/molecules
1 mol = molar mass of = any element or compound
moles → gramsgrams → molesmoles → atomsatoms → molesatoms → gramsgrams → atoms
There are six conversions: